Adding an extension is one of the most popular ways to improve a home. It gives you more space and can push up what your home is worth. But how much value does it actually add? The answer is: it depends. The type of build, where you live, and how the work is done all play a part.

This guide looks at the key things that affect the value an extension can add, what you might expect to get back, and what to think about before you start. If you are still deciding what to build, take a look at our extension ideas to improve your home’s value.

What affects how much value an extension will add?

Not all extensions add the same amount of value. Several things affect the result.

Type of extension

The type of extension you build has a big effect on the value it adds. Some of the most common types are:

  • Side return extension: This fills in the gap down the side of your home. It is a popular choice for terraced houses. It can add up to 15% to your home’s value.
  • Rear extension: This adds space to the back of the house. It is one of the most common types. It can add between 5% and 12% to your home’s value.
  • Loft conversion: This turns your loft into a room. It is often used as a bedroom or office. It can add up to 20% to your home’s value.
  • Garage conversion: This turns a garage into a living space. It tends to be one of the cheaper options. It can add around 10% to your home’s value.

Location and property market trends

Where you live has a large impact on how much value your extension will add. Homes in areas where prices are high tend to see a bigger rise in value from an extension. This is because buyers in those areas expect more space and are willing to pay for it.

In areas where house prices are lower, the cost of the build may be close to what it adds in value. It is worth checking local sold prices before you commit. A local estate agent can help you understand what buyers in your area want.

Quality of build and finishes

The standard of the work matters. A well-built extension with good finishes will add more value than one that looks cheap or rushed. Buyers will notice if the new space does not match the rest of the home.

Using skilled builders and good materials costs more upfront. But it tends to pay off when it comes to adding value and making the home easier to sell.

Size and use of the extension

Bigger does not always mean better. An extension that makes the home too large for its plot, or that takes up most of the garden, can put buyers off. The best extensions add useful space without harming what is already there.

Adding a bedroom or a larger kitchen tends to add the most value. These are the rooms buyers care about most.

What can I expect for my return on investment?

A return on investment, or ROI, is how much you get back compared to what you spent. For home extensions, the ROI varies a lot. Here are some rough figures to give you an idea:

  • Loft conversion: Can add up to 20% to your home’s value. Often one of the best returns.
  • Side return extension: Can add up to 15% to your home’s value. Works well in urban areas.
  • Rear extension: Can add between 5% and 12% to your home’s value. Good for open-plan living.
  • Garage conversion: Can add around 10% to your home’s value. Lower cost, decent return.

These are rough guides. The actual figure will depend on your home, your area, and the quality of the work. The best way to get a clear picture is to speak to a local estate agent before and after the build.

Things to consider to add value with an extension

Before you start, there are a few things worth thinking about:

  • Planning rules. Some builds need planning consent. Others fall under permitted development, which means you do not need to apply. Check with your local council before you start.
  • Budget. Set a clear budget and stick to it. Costs can rise if you change your mind partway through. Get more than one quote from builders.
  • Building regs. Even if you do not need planning consent, you will usually need to meet building regulations. These cover things like insulation, safety, and structure.
  • Kerb appeal. Think about how the extension will look from the outside. A build that clashes with the rest of the house can put buyers off.
  • Energy use. Good insulation and energy-efficient windows will keep your bills down and make the home more appealing to buyers.

How much does an extension cost?

The cost of an extension varies a lot. It depends on the size, the type, and where you live. For a more detailed breakdown, see our guide to house extension costs. Here are some ballpark figures:

  • Small single-storey rear extension: £20,000 to £50,000
  • Large single-storey rear extension: £50,000 to £80,000
  • Double-storey extension: £60,000 to £120,000
  • Loft conversion: £25,000 to £60,000
  • Garage conversion: £10,000 to £25,000

Costs are higher in London and the southeast. Always get a few quotes before you decide on a builder.

What adds more value, an extension or conservatory?

This is a common question. In most cases, a full extension adds more value than a conservatory. Here is why.

A conservatory is cheaper to build. But buyers often see it as a seasonal space rather than a true room. It can be too hot in summer and too cold in winter. This limits how useful it is and how much value it adds.

A full extension, built to the same standard as the rest of the house, is seen as proper living space. It can be used all year round. This makes it worth more to buyers.

That said, a well-built, insulated garden room or orangery that can be used all year can add good value. The key is that the space must feel like a proper part of the home.

Final thoughts

An extension can be a great way to add value to your home and get more out of the space you already have. The key is to plan well, use good builders, and think about what buyers in your area want.

If you are thinking about how to fund a house extension, a broker can help you find the right mortgage or loan for your situation. Pepper Money works with a network of brokers who can look at your options. Find a broker to get started.